Automatic electric circuit breakers



4 Sheets-Sheet 1 Filed Sept. 29. 1959' -FIG 2,

Pu1- FULL INVENTOR BR M N HAKG REAVEs ATTORNEYS April 1962 B. HARGREAVES AUTOMATIC ELECTRIC CIRCUIT BREAKERS 4 Sheets-Sheet 2 Filed Sept. 29, 1959 o T N E V m ATTORNEYS April 17, 1962 B. HARGREAVES AUTOMATIC ELECTRIOCIRCUIT BREAKERS 4 Sheets-Sheet 3 Filed Sept. 29, 1959 I NVENTOR BRMN HARGR EAVES BY W ATTORNEYS April 17, 1962 B. HARGREAVES 3,030,470

AUTOMATIC ELECTRIC CIRCUIT BREAKERS Filed Sept. 29. 1959 4 Sheets-Sheet 4 PUSH PULL INVENTOR BRiAN HA @REA\4Es' I My ATTORNEYS United States Patent OfiFice 3,030,470 Patented Apr. 17, 1962 3,030,470 AUTOMATIC ELECTRIC CIRCUIT BREAKERS Brian Hargreaves, 2 Central Drive, Ulverston, Lancashire, England Filed Sept. 29, 1959, Ser. No. 843,233 7 Claims. (Cl. 20088) This invention is for improvements in or relating to electric circuit breakers and temperature responsive electric switches.

One object of the invention is to provide a particularly compact or miniature circuit breaker.

A further object of the invention is to provide a fixed contact arrangement which will ensure good and reliable conductivity through the circuit breaker or switch.

According to one feature of the present invention there is provided an electric circuit breaker comprising a base part and a relatively movable lid or cover, relatively fixed and moving contacts, a latch or the like movably supported on the cover or lid and adapted to hold the moving contact in engagement with the fixed con-tact, and means responsive to overload conditions for releasing the moving contact from said latch or the like so as to allow the contacts to separate without movement of the cover (e.g. manually) to its open position also opening the circuit breaker.

According to a further feature of the present invention there is provided a temperature responsive electric switch comprising a temperature sensitive member carrying a contact adapted to be engaged between a pair of members, at least one of which is a contact, when the switch is closed, said temperature sensitive member being adapted to flex laterally, with respect to said pair of members,

so as to release itself from a holding member or detent' when the switch is required to open, the pair of members being arranged and/or constructed so that they do not interfere with said flexing movement of the temperature sensitive member.

In one embodiment of this feature of the invention the abutment members of said pair are arranged out of alignment one with the other. Alternatively or additionally one or both of the abutment members may be flexibly mounted.

In a preferred embodiment of the invention the circuit breaker includes a member or barrier of insulating material which, when the movable contact is released from the latch, takes up a position between the fixed and moving contacts. Conveniently this insulating member is a part of the latch.

The load sensitive means may comprise an electromagnet in the form of a loop located around a currentcarrying member of the circuit breaker. Additionally or alternatively there may be a load sensitive means .comprising a temperature responsive member through which current flows so that deflection of this temperature responsive member, at a predetermined overload current, will release the movable contact from the latch. Instead of passing the current through the temperature responsive member it may be located in proximity to a heater through which the current is arranged to flow.

The invention will be further described, by way of example, with reference to the accompanying drawings which show the invention applied to a miniature circuit breaker. In the drawings:

FIGURE 1 is a side elevation of the circuit breaker with the parts in the On position,

FIGURE 2 is a front view of the circuit breaker with the parts in the Tripped position but before the parts have been moved manually to an isolated position.

FIGURE 3 is a sectional view on the line IIIIII of FIGURE 4,

FIGURE 4 is a sectional View on the line IVIV of FIGURE 1,

FIGURE 5 is a side view of the circuit breaker with the parts in the position they occupy when the circuit breaker is moved manually to an isolated position,

FIGURE 6 is a front view showing a series of circuit breakers according to the invention neatly and compactly arranged in side-by-side relationship, and

FIGURE 7 is a side view showing how a circuit breaker according to the invention can be recess-mounted.

Referring to the drawing, the circuit breaker comprises a hollow base part 10 and a cover or lid 11 which is hinged to the hollow base part as indicated at 12. Conveniently the base part and lid are moulded to shape from insulating material. It will be noted from FIG- URES 2 and 4 that the base part and lid are of relatively narrow form so that the circuit breaker as a whole is of compact construction.

Mounted in the base 10 is a fixed contact assembly 13 (to be hereinafter described in detail) which is adapted to be connected to the external circuit by, by example, a plug and socket connecting arrangement as indicated at 14.

The movable contact assembly of the circuit breaker includes a bi-metallic arm 15 which is pivoted on the pivot pin 12 and is also adapted to be connected to the external circuit by, for example, a plug and socket type of connection as indicated at 140.

The switch mechanism includes a latch 16 of insulating material and having a latch part proper 17 adapted to engage a catch or part 18 on the switch arm 15, the latch being formed integrally with a tail part 19 for the purpose hereinafter to be described. The latch 16 carries an armature 20 adapted to be attracted by an electro-magnet formed by a split or open loop of magnetic material 21 arranged around the upper part 22 of the fixed contact assembly. Means may be provided for adjusting the air gap between the armature 20 and the loop of magnetic material 21.

The fixed contact assembly comprises two contact members proper 23 and 24. The member 24 may constitute a renewable arcing tip. The two contact members 23 and 24 are secured together towards the upper part of the fixed contact assembly.

The movable contact assembly of the circuit breaker comprises, in addition to the bi-metallic arm or blade 15 a resilient moving contact proper 25 which is of U-cross-section and is adapted to be engaged between the two members 23 and 24 of the fixed contact assembly. One of the limbs of the movable contact member 25 is extended upwardly as indicated at 26 in FIG- URE 4 and attached at its extremity by a bolt 27 to the upper extremity of the bi-metallic arm 15. The bimetallic arm 15 is arranged so that an increase in its temperature will cause it to flex in the direction of the arrow A (FIGURE 4) about the point 28. The lower part 1501 of the arm 15 need not necessarily be of bimetallic material and is more rigid than the part 15.

Located on the bolt 27 is a nut, having chamfered flats, which forms the catch or part 18, previously referred to, adapted to be engaged by the latch proper 17. The nut 18 may be adjusted along the bolt 27 to obtain a desired setting of the circuit breaker and is held in any position of adjustment by means of a leaf spring 29.

The flow of current through the circuit breaker is by way of the fixed contact members 23, 24, the contact 25, the arm 26, the bi-metallic arm or member 15, 15a, and a bracket 30 which carries the pivot 12 and is connected to the terminal point 14a.

Movement of the arm 15 automatically to the Off position when the circuit breaker is tripped, is halted by a stop 31, carried by the base part 10, which stop is adjustable so that the blade can be positioned correctly With respect to the other operating parts of the circuit breaker.

The cover 11 is releasably held in the closed position by, for example, a leaf spring 32 secured to the base part and having a part 33 adapted to snap under an abutment part 34 on the cover or lid.

The arm 15 is held in the closed position of the circuit breaker against the action of a spring 35 anchored at 36 to the arm 15 and at 37 to the cover or lid 11.

The operation of the circuit breaker above described is as follows:

In the closed position of the circuit breaker as shown in FIGURE 1 it will be noted that the latch 17 is in engagement with the catch 18 so as to hold the arm 15 and the moving contact assembly in the closed position against the action of the spring 35 which is under tension. It will also be noted that the armature 20 on the latch member '16, 17 lies immediately under, but spaced from the electro-magnet 21.

On the occurrence of a short circuit or other condition resulting in a momentary very heavy current flow, the armature 20 will be attracted to the magnet 21 and as a result the latch 17 will release the catch 18 and the movable contact assembly, under the action of the spring 35, will fly to the Off position as indicated in FIGURE 3. It will be noted that the pivoted latching member 16 in following movement of the movable contact means to the open position, takes up a position in which it tends to inhibit arcing, the weight of the latch proper 17 and of the armature 20 serving to bias the latching member to this position. The tail piece 19 of the latch member 16 may bear on its face 38 (see FIGURE 3) the inscription Trip which becomes visible through a window 39 in the lid 11.

Under prolonged overload conditions of a relatively moderate character not sufficient to operate the electromagnet 20, 21, there will be an increase in the temperature of the bi-metallic arm 15 and eventually when these overload conditions approach a predetermined limit the arm 15 will have flexed in the direction of the arrow A (see FIGURE 4) to such an extent that the catch or nut 18 will release itself from the latch 17 and the movable contact assembly will then fly into the open position under the action of the spring 35 and the parts will again take up the position indicated in FIG- URE 3.

It will be appreciated from What has just been stated that the circuit breaker above described takes care not only of sudden heavy overloads such as result from short circuit conditions but also prolonged moderate overloads if the period of such overloads becomes dangerous.

It will be noted from FIGURE 2 that even when the circuit breaker has tripped the indication On a part 4% of the base 10 is still visible through an aperture 41 provided on the lid 11 (see FIGURE 3). This is a safety precaution and in order to isolate the circuit breaker it is necessary to swing the lid member 11 outwardly as shown in FIGURE against the action of its holding spring 33. Even if the circuit breaker should accidentally have stuck in (due to having been used on more onerous loads than those to which it is intended), this will ensure that it is moved physically to the open position, having regard to the fact that the latch member 16, 17 is attached to the movable lid 11.

In order to re-set the circuit breaker after it has tripped, it is necessary first to move the lid 11 to the position shown in FIGURE 5. In this position it will be noticed that the latch 17 has become re-engaged with the catch 18. Consequently when the lid 11 is moved forwardly again into the closed position the latch will push the movable contact arm 15 into the closed position and will hold it in this position until released either by the operation of the electro-magnet 20', 21 or the bi-metallic arm 15.

It will be noted that the actual contact surfaces of the contacts 23 and 24 (which are indicated diagrammatically in FIGURE 4) are located out of alignment with one another. This enables the arm 15 to flex about the point 28 without undue interference by the contact members 23, 24. If these contact members were arranged in alignment by, for example, locating the contact 23 at 23a as indicated in FIGURE 4, there might be serious interference with the movement of the bi-metallic arm 15 and the circuit breaker would probably fail to operate. This contact arrangement can be applied'with advantage to temperature responsive switches other than circuit breakers.

A series of circuit breakers as above described may be assembled compactly side by side as shown in FIGURE 6 and conveniently they are attached to a common supporting bar by clips or the like so that any one circuit breaker can be removed easily when required. Preferably each circuit breaker or the several circuit breakers will be enclosed behind a front cover having a removable front plate with an opening just sufficiently large to enable the lid 11 to be pulled outwardly when required.

In the arrangement shown in FIGURE 7 the circuit breaker is mounted in a cavity or recess behind a front plate 42 and it will be noted that the lid 11 projects by only a small amount beyond the front plate. The latter has an opening 43 to permit the lid 11 to be moved from the closed to the open position and vice versa. The body of the circuit breaker 10 is supported on a bar 44, which may carry several circuit breakers in side-by-side relationship by means of a clip 45 on each circuit breaker.

- The circuit breaker can, of course, be operated manually by means of the lid 11 from the closed to the open position, i.e. the lid will be moved from the position shown in FIGURE 1 right through to the position shown in FIGURE 5. In this case the opening action will be relatively slow and the insulating part 16 of the trip member will not be interposed between the fixed and moving contacts. In the position shown in FIGURE 5 the On indication is covered by the lid. By having. the On position showing when the contactor has tripped but not when it has been opened manually, it is possible to discriminate on rapid inspection of several circuit breakers between those which have opened automatically due to a fault or overload and those which have been opened by hand.

Whilst the invention has been described more particularly as applied to a single pole electrical circuit breaker, it will be appreciated that it can be applied to multi-pole circuit breakers.

The adjustable screw 31 also forms a stop for limiting outward movement of the cover 11 to its open position as shown in FIGURE 5.

The lid 11 may be provided with a recess or other device or devices to enable it readily to be gripped by the hand to facilitate movement of it to the open position.

It will be appreciated that the circuit breaker need not necessarily incorporate operation by both a temperature sensitive member and an electro-rnagnetic means. It may incorporate one or the other or both as desired. It will be appreciated, however, that 'where the circuit breaker is provided with both a temperature sensitive control and electro-rnagnetic operation, there will be an integrating effect between the two which has certain advantages. In this connection it should be noted that the catch-nut 18 is chamfered so that as it is moved laterally by the temperature sensitive member there can be, ifdesired, progressive decrease in the amount the latch 17 must lift under the action of the electro-magnet 21 in order to release said catch-nut and thereby the arm 15.

An arc barrier 46 (see FIGURE 4) may be provided to protect the latch 17.

The circuit'breaker may include within its casing an early making late breaking neutral switch (i.e. a' switch.

in a neutral link through the circuit breaker) adapted to be operated by the main moving contact.

I claim:

1. An electric circuit breaker comprising a base part, fixed contact means on said base part, movable contact means having a pivotal support on said base part and operative to engage said fixed contact means, a spring acting to disengage the fixed contact means from the moving contact means, a cover enclosing said fixed and movable contact means, means pivotally supporting said cover on the base part, a latch pivotally supported on said cover, a catch on the movable contact means engageable by said latch so that the latter holds the movable contact means in engagement with the fixed contact means against the action of said spring so long as the cover is closed, said latch having a bias so that it follows movement of the movable contact means to an open position under the action of said spring, electric-load sensitive means operative to disengage said latch and catch on the occurrence of an overload, the latch, when following movement of the movable contact means to the open position, positioning itself so that when the cover is swung about its pivot to open the circuit breaker said latch and catch reengage and the cover is operative when moved back to its closed position to re-engage the movable contact means with the fixed contact means, the cover also being operative when moved to its open position and if the latch and catch are engaged to open the circuit breaker.

2. An electric circuit breaker comprising a base part, fixed contact means on said base part, movable contact means having a pivotal support on said base part and operative to engage said fixed contact means, a spring acting to disengage the fixed contact means from the moving contact means, a cover enclosing said fixed and movable contact means, means pivotally supporting said cover on the base part, a latch including an arc barrier part of insulating material pivotally supported on said cover, a catch on the movable contact means engageable by said latch so that the latter holds the movable contact means in engagement with the fixed contact means against the action of said spring so long as the cover is closed, said latch having a bias so that it follows movement of the movable contact means to an open position under the action of said spring, electric-load sensitive means operative to disengage said latch and catch on the occurrence of an overload, the latch, when following movement of the movable contact means to the open position, positioning itself so that the arc barrier part lies between the fixed and movable contact means and when the cover is swung about its pivot to open the circuit breaker said latch and catch re-engage and the cover is operative when moved back to its closed position to re-engage the movable contact means with the fixed contact means, the cover also being operative when moved to its open position and if the latch and catch are engaged to open the circuit breaker.

3. An electric circuit breaker comprising a base part, fixed contact means on said base part, movable contact means having a pivotal support on said base part and operative to engage said fixed contact means, a spring actting to disengage the fixed contact means from the moving contact means, a cover enclosing said fixed and movable contact means, means pivotally supporting said cover on the base part, a latch pivotally supported on said cover, a catch on the movable contact means engageable by said latch so that the latter holds the movable contact means in engagement with the fixed contact means against the action of said spring so long as the cover is closed, said latch having a bias so that it follows movement of the movable contact means to an open position under the action of said spring, electric-load sensitive means comprising an electro-magnet in the form of a loop of magnetic material located around a current carrying member of the circuit breaker and a temperature responsive member and heating means therefor through which current through the circuit breaker flows and operative to disengage said latch and catch on the occurrence of an overload, the latch, when following movement of the movable contact means to the open position, positioning itself so that when the cover is swung about its pivot to open the circuit breaker said latch and catch re-engage and the cover is operative when moved back to its closed position to re-engage the movable contact means with the fixed contact means, the cover also being operative when moved to its open position and if the latch and catch are engaged to open the circuit breaker.

4. An electric circuit breaker comprising a base part, fixed contact means on said base part, movable contact means including a temperature responsive part and having a pivotal support on said base part and operative to engage said fixed contact means, a spring acting to disengage the fixed contact means from the moving contact means, a cover enclosing said fixed and movable contact means, means pivotally supporting said cover on the base part, a latch pivotally supported on said cover, a catch on the movable contact means engageable by said latch so that the latter holds the movable contact means in engagement with the fixed contact means against the action of said spring so long as the cover is closed, said latch having a bias so that it follows movement of the movable contact means to an open position under the action of said spring, a heater means in proximity to the temperature responsive part of the movable contact means and through which current through the circuit breaker flows and operative by flexing said part laterally to disengage the catch from the latch on the occurrence of a prolonged moderate overload, electric load sensitive means comprising an electro-magnet operative by moving the latch to disengage said latch and catch on the occurrence of a short-circuit overload, the latch, when following movement of the movable contact means to the open position, positioning itself so that when the cover is swung about its pivot to open the circuit breaker said latch and. catch re-engage and the cover is operative when moved back to its closed position to re-engage the movable contact means with the fixed contact means, the cover also being operative when moved to its open position and if the latch and catch are engaged to open the circuit breaker.

5. An electric circuit breaker as claimed in claim 4 wherein the catch is chamfered.

6. An electric circuit breaker as claimed in claim 4 and having two fixed contact members which receive the movable contact between them, said fixed contacts being located out of alignment whereby they do not interfere with the flexing movement of the temperature responsive member.

7. An electric circuit breaker as claimed in claim 4 and having two fixed contact members which receive the movable contact member between them, at least one of said movable contact members having a flexible mounting so as not to interfere with the flexing movement of the temperature responsive member.

References Cited in the file of this patent UNITED STATES PATENTS 2,210,263 Sachs Aug. 6, 1940 2,229,842 Frank Jan. 28, 1941 2,330,237 Platz Sept. 28, 1943 2,787,682 Lochcr Apr. 2, 1957 

